Device for proactive modulation of cardiac strain patterns

ABSTRACT

A direct cardiac assist device which may aid in ventricular recovery. The device proactively modulates cardiac strain pattern to produce a contraction strain pattern that induces beneficial growth and remodeling of the myocardium or prevents or reduces apoptosis of the myocytes. The device may include an outer shell. membrane, or mesh and an inner membrane. The space between the outer member and the membrane may be filled with fluid that is pressurized during contraction. The device prescribes a beneficial strain pattern during heart contraction. This strain pattern does not invert the curvatures or grossly alter the curvatures of the heart and may assist in myocyte regrowth and healing of the failing heart.

PRIORITY CLAIM

The present application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application Ser. No. 60/479,625 filed Jun. 18, 2003.

TECHNICAL FIELD

The present invention is related in general to a direct cardiaccompression device. In particular is a direct cardiac compression devicethat proactively modulates the strain pattern in the heart duringcontraction so as to reduce apoptosis in the myocardium and/or inducebeneficial growth and remodeling of the myocardium and/or scarredregions. In particular, the device of the present invention does notinvert or grossly perturb the curvature of the hear during contraction.In so doing this invention may promote recovery of the heart frominjury, ischemia, infarction, infection, and/or congestive heartfailure; and when combined with pharmacotherapy, pacing, electricalresynchronization, surgical reconstruction, stem cell therapy, genetherapy, and/or other therapies, it may further enhance recovery of theheart.

BACKGROUND OF THE INVENTION

Congestive heart failure (CHF) is a debilitating condition that afflicts4.8 million Americans with an increasing incidence. Despite efforts atpreventative cardiac care, the incidence of CHF is increasing becausethe average age of survival in the population is increasing and becausemore people are surviving their first heart attack. Pharmacologicaltherapy and electrical stimulation therapies are improving, yet manypatients still reach end-stage heart failure. Heart transplant isavailable for some patients with the most severe heart failure, howeverthe supply of donor hearts is not adequate to meet demand and there aremany complications associated with immunosuppression. Aberrant growthand remodeling are evident in CHF, and it is likely that growth andremoding are primary contributors to infarct expansion, myocardialscaring, and ventricular rupture.

Recent studies show that effective (i.e., physiological) growth andremodeling of the heart's muscular tissue can reverse and cure CHF insome patients. Such a cure of CHF is called “ventricular recovery”herein, yet in some literature it is called reverse remodeling. Themechanism of ventricular recovery is a current and active area ofresearch for the treatment of CHF. Hormonal and electro-physiologicalfactors may play an important role. In addition, the influence ofventricular loading conditions on CHF is a significant factor. Unloadingthe diseased heart may decrease end-systolic volume and may create amore physiological strain pattern of the heart. A physiological strainpattern during contraction (also called “systole”) may lead toventricular recovery, and it may prevent infarct expansion, myocardialscarring, and/or ventricular rupture.

Further evidence for a potential, fundamental role of strain in cardiacphysiology and pathophysiology is that myocytes are highly sensitive tostrain and respond with altered gene expression. (See Komuro and Yazaki,Ann. Rev. Physiol. 55:55-75(1993) and Sadoshima and Izumo, Ann. Rev.Physiol. 59:551-571(1997).) Numerous investigations have shown thataltered hemodynamic loading and/or heart disease lead to growth andremodeling of myocytes and their extra-cellular matrix. It is also knownthat failing hearts exhibit a patho-physiological strain pattern wherehoop strain and apex-base stain are more equal than normal and heartwall thickening during contraction is globally less than normal and moreuniform across the wall. Although there is still debate on what is thenormal motion or strain pattern during contraction, current results showa strain pattern wherein hoop strain is greater than apex-base strainand greater wall thickening is seen on the inner wall of the heart ascompared to the outer wall.

Thus the present invention includes a method of restoring a more normalphysiological strain pattern to a dyskinetic or failing heart, i.e. aheart with a patho-physiological strain pattern. By doing so, myocytesmay be induced to grow in a normal manner. The effects on stress andstrain on myocyte growth is described in greater detail in J. H. Omens,“Stress and strain as regulators of myocardial growth”, Prog. Biophys.Mol. Biol.,69(2-3:559-72 (1998).

Despite the promise shown by growth and remodeling of damaged ordiseased heart tissue, there have been no known attempts to proactivelymodulate the strain pattern during contraction. Instead, treatments havebeen focused on ways to increase blood flow, off-load the heart, and/orreduce wall stress. These methods include some blood contacting assistdevices, surgical reconstruction of the ventrilcle(s), cardiomyoplasty,and surgical insertion of passive devices. These treatments may promotea more healthy type of strain pattern during contraction, yet they do soindirectly if at all.

Current devices that provide direct mechanical assistance to the heartitself are often called direct cardiac compression devices (DCCDs), andthey do modulate directly the kinematics during contraction. Yet currentDCCDs do not proactively modulate the strain pattern so as to guideheart recovery and/or myocardial recovery. In contrast, many devices maycause detrimental remodeling and/or apoptosis because the induced strainpattern is so grossly abnormal. As is clear from the various patents andpapers on these devices, current DCCDs have been optimized to promotesystolic ejection, to be implanted easily, to reduce thrombo-emboliccomplication, to closely fit the heart contours during diastole, andcriteria other than systolic strain pattern modulation.

An extremely important aspect of contraction strain pattern is the factthat it depends on both the end-diastolic configuration (referenceconfiguration) AND the end-systolic configuration (currentconfiguration). The strain field is a function of the gradient (withrespect to reference position) of the mapping of material points fromthe reference configuration to the current configuration. Thus, the factthat prior DCCDs have tried to fit well the diastolic configuration isinconsequential to achieving an appropriate contraction strain patternbecause their end-systolic configurations are either grossly aberrant orunknown.

First, an early DCCD (called a cardiac massager because it was designedfor use in open chest surgery and not for implantation) developed byVineberg is described in U.S. Pat. No. 2,826,193 (the Vineberg patent).This device, when inflated, produces a systolic state with low (or eveninverted) curvature in the circumferential-radial plane of the heart(FIG. 2, Vineberg patent) and in the longitudinal-radial plane (FIG. 3,Vineberg patent). This is caused by the two opposite chambers which,when inflated, induce hourglass-like systolic geometries (FIG. 5,Vineberg patent). Thus the vineberg device induces an aberrant strainpattern during contraction.

A later device, the Anstadt cup, is described in U.S. Pat. No. 5,119,804(the Anstadt patent). This device induces an inverted curvature of thelongitudinal-radial plane during systole, but does retain a normalcircumferential-radial plane curvature during systole (FIGS. 8, 9, and10 Anstadt patent). The CardioSupport System made by Cardio Technolgies,Inc. is similar to the Anstadt cup and also induces curvature inversionin the longitudinal-radial plane.

Whereas the Anstadt cup inverts curvature in the longitudinal-radialplane, the heart booster (U.S. Pat. No. 5,713,954 and Ann. Thorac. Surg.68:764-7) inverts curvature in the circumferential-radial plane, but notin the longitudinal-radial plane (FIGS. 1 and 2, Ann. Thorac. Surg.68:764-7). This device prescribes a gear-like geometry with numerousspurs. Each spur in this end-systolic geometry induces curvatureinversion during systole.

The Anstadt cup and heart booster attach to the apex of the heart, whilethe Vineberg device attaches to the base through a draw stringcontstrictor at the valve plane. However, many other DCCDs attach to theinterventricular grooves and either pull on the grooves (for example,the AbioBooster by Abiomed, Inc., Danvers, Mass. as described by Karvanaet al., 2001, and the DCC Patch by Heart Assist Technologies, New SouthWales, Australia) or hold them static (for example the device in U.S.Pat. No. 4,536,893 of Parravicini, the “Parravicini patent”). In eithercase, pulling or holding the grooves static likely decreases thecurvature in the circumferential-radial plane during systole whereas fornormal hearts curvature increases as the diameter decreases duringsystole. (Note that the radius-of-curvature R is the inverse ofcurvature C, i.e. C=1/R). Nevertheless, it is uncertain what thesystolic configuration is for these devices because it is not disclosed.

The Abiobooster and DCC Patch cover one ventricle of the heart, and itis likely that when pressurized they decrease the curvature of the freewall and septum. The Parravicini device is sutured to theinterventircular groove (or sulcus) and either pulls on the groovesusing the two opposing membranes or is held static by the outer rigidshell. Again, the exact mode of operation is not clear from theParravicini patent because a systolic configuration is not shown. Ineither case, the resulting strain pattern is not proactively modulatedand a decrease in curvature likely occurs during contraction.

One embodiment (shown in FIG. 3, but not FIGS. 1 and 2) of the Hewsondevice shown in U.S. Pat. No. 3,034,501 (the Hewson patent) is similarto the Vineberg and Parravicini devices in that two opposing membranessquash the heart and tend to flatten it between the opposing membranes(i.e. induce a systolic configuration with decreased curvature in muchof the circumferential-radial plane yet with dramatically increasedcurvature on the edges where the two membranes attach to the device).However, a systolic configuration is not shown.

Similarly, a systolic configuration is not shown for the embodiment ofthe Hewson device in FIGS. 1 and 2 of the Hewson patent. To derive asystolic configuration, one must consider a force balance with thepneumatic chamber pressurized. Upon doing a force balance, however, onerealizes that the Hewson embodiment 1 is unrealistic and notimplantable. A pressure P in the pneumatic chamber will induce at leastan upward force of PA where A is the cross-sectional area of the openingrim. If there are tensile membrane stresses the upward force will behigher. Hewson suggests that contact forces between the rim and theheart are supposed to hold the heart in place, yet even active heartsare soft tissues that can undergo high shear and slip out of the Hewsondevice. Moreover, it is now known that myocardium is organized intosheets that allow contracting myocytes to rearrange and shear to attainhigh radial strains-i.e., motions that would allow the heart to slip outof the Hewson device. A hypocontractile or failed heart would be evenmore likely to slip out because it would more easily permit radialstain.

To evaluate this problem, a device similar to that of Hewson wasconstructed and implanted in a young bovine. Ultrasound measurements ofthe actual animal were used to precisely size the device. Even withnormal contractility (i.e. high stiffness), the heart readily escapedfrom the device. The valve plane had to be sewn to the device and heldin place with a stent that went from the device through the transversepericardial sinus and pushed down on the commisure of the aortic andbicuspid valves.

Although a number of DCCDs are described above, other examples may beknown to one skilled in the art. However, all current operable DCCDssuffer from a tendency to increase or even invert the curvature of theheart and thus produce an aberrant strain pattern during contraction.

SUMMARY OF THE INVENTION

The present invention includes a DCCD that proactively modulates thecardiac strain pattern during contraction or systole. Proactivemodulation of cardiac strain pattern includes active promotion of astrain pattern that induces growth and remodeling of the myocardium,diseased myocardium and/or scarred myocardium to more closely resemble ahealthy myocardium and/or that reduces apoptosis in the myocardium. Inall embodiments of the invention, the strain pattern during systole isproactively modulated. Although clinical trials and animal experimentswith this invention will determine what strain pattern is morebeneficial, current results suggest that the native strain patternshould be restored which is one with circumferential strain morenegative than apex-base strain and with radial strain highest on theinner wall. In general, devices of the present invention do not invertthe curvature or greatly perturb the curvature of the heart duringcontraction. The invention also may maintain the normal curvatures orstrain pattern during diastole, or relaxation of the heart.

In one embodiment, the DCCD includes a membrane or mesh that encompassesthe heart and that undergoes a shape change from an end-diastolicconfiguration to an end-systolic configuration and back again. Theseconfigurations and the way in which the shape change occurs are designedto promote a beneficial strain pattern in the heart during contraction.

In a further embodiment, the DCCD may include an outer shell, membrane,or mesh and an inner membrane attached to the outer shell. A fluid,which may be pressurized, may be provided between the outer shell andinner membrane.

In still further embodiments, the DCCD may be installed around theventricular portion of a heart. It may be anchored to the valve plane ofthe heart. The device may include a pneumatic drive operable topressurize the fluid.

In certain embodiments of the device, the outer shell, membrane, or meshmay be rigid, or it may include an adjustable outer shell, membrane, ormesh and/or inner shell, membrane or mesh.

A DCCD of the present invention may be used to assist a heart byattaching the device to the heart. Attaching any DCCD as described aboveor otherwise within the scope of the present invention may also assistin: ventricular recovery, providing a normal physiological strainpattern to the heart, particularly during systole, promoting normalmyocyte growth in the heart, preserving the myocardium in the borderzone of acute infarcts, preventing ventricular rupture in the few daysfollowing a myocardial infarction, reducing scar formation and promotinggrowth of myocytes from native or injected myoblasts in infarcted hearttissue, restoring heart function after myocardial infarction, andgenerally promoting beneficial growth and remodeling of the cardiactissue, particularly to attain ventricular recovery, in patients withheart insufficiency resulting from acute or chronic causes, inter alia.

DCCDs of the present invention may be employed for any of the usesdescribed above, or for other uses in which a physiological strainpattern during systole is beneficial, by providing the device to apatient. This may be accomplished by opening the chest cavity of thepatient to provide access to the heart and attaching the device to theheart. For devices that expand once inside the chest, they may beprovided through a smaller incision or through a tube. In someembodiments, the device may be anchored to the valve plane of the heart.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete and thorough understanding of the present embodimentsand advantages thereof may be acquired by referring to the followingdescription taken in conjunction with the accompanying drawings.

FIG. 1 illustrates an embodiment of the DCCD of the present inventionapplied to the ventricular surfaces of the heart.

FIG. 2 illustrates the construction of a prototype of an embodiment ofthe present invention. The prototype was built to fit the heart of a 110kg young bovine into which the device was implanted for an acute period(2 hours) to test the valve plane attachment and the preservation ofcardiac curvature during assist with varying degrees of heart failure(induced pharmacologically with high doses of a beta-blocker). Becausethe period of implantation was brief, biocompatible materials were notutilized; rather inexpensive and readily available materials were used.

FIG. 2 a represents 5 measurements of the bovine heart made by cardiacultrasound and the Left Ventricle Free Wall Profile (LVFWP).

FIG. 2 b represents a 3D shell generated by sweeping the LVFWP about anaxis in a non-axis-symmetric manner.

FIG. 2 c depicts an outer shell of the prototype formed using matchingmolds with epoxy reinforced with fiberglass.

FIG. 2 d depicts a side view of the completed prototype.

FIG. 2 e depicts a top view of the completed prototype.

FIG. 3 illustrates a prototype embodiment of the DCCD of the presentinvention in which a bovine heart is attached. Running sutures form acomplete ring of attachment. Half of the suture attachment loops are notused. The run patterns is: two forward loops while going through thetissue then back one loop before doing another forward bite.

FIG. 4 illustrates a prototype embodiment of the DCCD of the presentinvention in which a bovine heart is attached. The method of attachmentshown avoids sutures near the anterior and posterior interventricularsulci. The posterior stent would lie oblique to the pericardial sinusand go through the pericardial reflections to connect with an anteriorstent that lies in the oblique pericardial sinus.

FIG. 5 illustrates an embodiment of the DCCD of the present inventionapplied to the ventricular surfaces of the heart.

FIG. 6 illustrates an embodiment of the DCCD of the present inventionwith an adjustable outer shell.

FIG. 7 illustrates a cut-away view of an embodiment of the DCCD of thepresent invention with an adjustable outer shell.

FIG. 8 illustrates an embodiment of the DCCD of the present inventionapplied to the ventricular surfaces of the heart.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a DCCD for proactive modulation ofcardiac strain pattern. Proactive modulation of cardiac strain patternaccording to the present invention includes the active promotion by aDCCD of a strain pattern that induces growth and remodeling of themyocardium to more closely resemble a healthy myocardium or that reducesapoptosis in the myocardium.

In most embodiments of the invention, the strain pattern is aphysiological strain pattern. A physiological strain pattern, for thepurposes of the present invention, is one which does not invert theheart's curvature during systole. The invention may also maintain anormal curvature or strain pattern during diastole, or relaxation of theheart.

Such DCCDs may be formed in a variety of ways, but generally include amembrane or mesh that encompasses the heart and that undergoes a shapechange from an end-diastolic configuration to an end-systolic one andback again. These configurations are such that they promote a desiredstrain pattern, such as one in which the epicardial contours or heartcurvatures are optimized. Other aspects of strain such as cardiac twistmay or may not be modulated.

In one embodiment, there is an outer shell, membrane, or mesh, such as arigid outer shell, attached to an inner membrane and filled with a fluidthat may be pressurized during systole to assist the heart whilepreserving a beneficial strain pattern and not inverting the curvatureof the heart.

In one embodiment of the present invention, the DCCD is designed to fitaround the ventricular surface of the heart as shown in FIG. 1. Briefly,the DCCD 10 includes an outer rigid shell 12 attached to the valve plane14 of the heart 16, a highly elastomeric membrane 18 which abuts theepicardial surface of the heart 20 and modulates extra-ventriculardisplacements, and fluid 22 between the shell 12 and membrane 18 whichis pressurized during systole to assist the heart. The device may be runpneumatically, for example with a system similar to that used with theAnstadt cup. Methods of producing such a device are provided in Example1.

In another embodiment of the present invention, a DCCD is designed tofit around the ventricular surface of the heart as shown in FIG. 5. TheDCCD 30 is similar to that of FIG. 1, except that at least oneadditional woven component 32 is provided between the elastomericmembrane 18 and the shell 12. These woven components are referred toherein as “socks” 32 and preferably do not have a symmetrical weave. Thesocks 32 instead have a satin weave with a directional bias with morefibers in the apex-base direction to make the apex-base motion less thanthe circumferential motion. The weave may also have a helical componentto give the heart a twist when it is in its dilated or diastole state.To increase the amount of anisotrophy, longitudinal fibers in the socksmay be thicker than circumferential ones. As the heart heals, at leastpartially as a result of the physiological strain patterns produced bythe DCCD, and returns to normal size, the outer socks will collapse andnot modulate the strain pattern. This gradually weans the healing heartfrom the DCCD.

In addition to the use of socks, the embodiment of the invention in FIG.5 preferably uses a biocompatible inner membrane 34 abutting theepicardium 20. The membrane 34 may be isotropic and homogeneous. Forexample, a segmented polyurethane membrane as used in aortic balloonsmay be used. In order to produce a composite structure of membrane andsocks that is anisotropic and heterogeneous and able to restore aphysiological strain pattern to the heart, the socks 32 may beanisotropic and have a weave that may vary with circumferential and/oraxial location.

Yet another embodiment of the DCCD of present invention is shown inFIGS. 6 and 7. The embodiment 40 is adjustable as the diseased heartrecovers. The embodiment lacks a rigid outer shell and instead includesan adjustable shell 42 formed from a series of rods 44 attached to abasal annulus 46 and attached to or passing through an apical annulus48. The basal annulus 46 is designed to fit the valve plane of theheart, which does not vary significantly between diseased andnon-diseased states. The rods 44 are bent to form a vase-shapedstructure as shown in FIG. 6. Elastic membranes 50 and 52 may be used toseal the adjustable shell 42. Specifically, one membrane 50 may beplaced on the inside of the shell 42 and one on the outside 52, as shownin FIG. 7. These membranes 50 and 52 may be held in place by applying anegative pressure to the space in which the rods 44 lie. Use of largernumbers of rods minimizes puckering of the membranes 50 and 52 whenpressure is applied between the shell and the inner membrane. Themembranes 50 and 52 may be woven or non-woven.

To decrease the size of the shell 42 as the heart heals, the apicalannulus 48 may be pulled into a flared tube-like structure 54 as shownin FIG. 7. Lead screws (not shown) may be used to pull on the apicalannulus 48 and draw it into the tube 54. These screws may be turnedusing a custom designed catheter. When implanted in a human, the lowertube-like structure 54 may be placed along the inferior boundary of theleft lung. A pneumatic driver (not shown) may be placed in the abdomen.

Yet another embodiment of the DCCD of the present invention is shown inFIG. 8. In this embodiment the device 60 includes a functionally-gradedmembrane 62 surrounding the heart 16 with a hard shell 64 enclosing themembrane 62. The shell 64 may be attached to the valve plane 14. Amagnetic piston 66 at the bottom of the shell 64 may be driven by asolenoid (not shown) to change the volume within the shell 64 and assistejection and/or filling of the heart 16 with blood. There may be apermanent magnet (not shown) in the shell 64 so that the piston 66 isdrawn outward to counteract the resting tension in the membrane 62 thatsurrounds the heart 16. An outer membrane filled with nitrogen or aninert fluid may be included to prevent body fluids from entering thesolenoid-piston interface and to prevent the piston 66 from impacting ordrawing in other organs (i.e. lung or diaphragm). The device 60 may alsoinclude wires and electrical components (not shown) that sense theelectrocardiogram or pace the heart and simultaneously drive the piston66 such that piston action and the heartbeat are synchronized.

In another embodiment of the present invention, not explicitly shown,the DCCD includes biocompatible chamber(s) that attach together and thatslip over the apex of the heart and contain the ventricles. The chambersmay be structured so as to take on shapes that proactively modulatesystole strain patterns in a beneficial manner. They may alsobeneficially modulate diastolic strain patterns.

In other embodiments of the present invention, not explicitly shown,current devices may be modified to resemble the devices described aboveor to otherwise render them able to proactively modulate cardiac strainpatterns during systole. For example, in all devices that pull on theinterventricular grooves and in the Hewson device, the balance of forcesmay be examined to determine a systolic configuration geometry that willproactively modulation the strain pattern in accordance with the presentinvention.

For DCCDs that attach to the apex of the heart, such as the Anstadt andCardioSupport System, it is possible to make them proactive modulatorsof strain patterns according to the present invention by making thesuction cup deformable and such that it preserves cardiac curvature whenthe air chambers are pressurized.

For the heart booster, it is possible to make it a proactive modulatorof contraction strain pattern by increasing the number of tubes so thatthe curvature inversion is insignificant or introduce a membrane thatsurrounds the heart and has a liquid between it and the tubes. The fluidwill fill then flow into the spur regions rather than pull in themyocardium. Other ramifications are possible so long as the systolicconfiguration is optimized for strain pattern.

Other ramifications of existing devices are possible that optimize thesystolic configuration to obtain a strain pattern in accordance with thepresent invention. In some embodiments, this may limit optimization forejection of blood, a primary design goal in such devices. However, solong as a suitable amount of blood is ejected initially, therebypreventing serious harm to the patient, blood ejection will oftenimprove as the myocardium heals in response to the physiologicalsystolic strain patterns.

Various metals or other hard materials may be used to form components ofselected embodiments of the present invention. In certain embodiments,titanium, Nitinol (a shape memory titanium/nickel alloy) and/or or hardbiocompatible plastic may be used to from any rigid components. Forexample, titanium may be used to form stents because it is strong,light, and biocompatible. Nitinol may be used if the stent may be bentout of shape during insertion. A rigid outer shell in certainembodiments may be made of titanium or a hard biocompatible plastic likethat of the casing of current artificial hearts such as The AbioCorTotal Artificial Heart.

Additionally in selected embodiments with socks, the elastomeric fibersin the socks may be elastomeric polyurethane. Membranes may be made ofelastomeric polyurethane. Such membranes are durable, biocompatible, andare capable of high strain and are used in current DCCDs and aorticballoons.

A patient with a heart that is growing aberrantly is in need ofintervention to prevent progression to end-stage heart failure. Ifpharmacotherapy is ineffective, then cardiac assistance with a DCCD ofthe present invention may reverse the aberrant growth by inducing abeneficial type of deformation to the heart during systole. In somepatients ventricular recovery (re-growth of a healthy heart) is evenpossible.

The present invention thus includes implanting DCCDs of the presentinvention in a patient in order to promote beneficial cardiac remodelingand growth or prevent myocyte apoptosis, or for other reasons beneficialto the patient. This implantation may be accompanied by othertreatments, such as pharmacotherapy, pacing, electricalresynchronization, surgical reconstruction, stem cell therapy, genetherapy, and/or other therapies.

Methods of the present invention may also include using a DCCD of thepresent invention for systolic compression near the beginning ofsystolic ejection when the heart is full and its thickness-to-radiusratio is lowest. The length of systolic compression may be varied withthe device used and the needs of the patient. In an exemplaryembodiment, compression lasts between 55-60% of systolic duration.Similarly, the amount of pressure applied during compression may bevaried depending upon the patient's needs.

The following examples are provided to further explain specific examplesof the invention. They are not intended to represent all aspect of theinvention in its entirety. Variations will be apparent to one skilled inthe art.

EXAMPLES Example 1 Formation of a Prototype DCCD

A prototype of one embodiment of the present invention was built to fita 110 kg bovine into which the device was implanted for an acute period(2 hours) to test the valve plane attachment and the preservation ofcardiac curvature during assist with varying degrees of heart failurewhich was induced pharmacologically with high doses of a beta-blocker.Because the period of implantation was brief, biocompatible materialswere not utilized; rather inexpensive and readily available materialswere used. The methods of construction and sizing are directlyapplicable to devices for use in humans or other animals.

The size of this device was determined by 5 cardiac measurements—all ofwhich can be made via a cardiac ultrasound. The major diameter (D_(maj))and minor diameter (D_(min)) were obtained from a short axis view in theequatorial region. From a long axis view one can obtain: AB-distancefrom apex to base; EB-distance from equator (fattest part) to base; andR₁—radius of curvature of the apex. As diagramed in FIG. 2 a, thesemeasurements were used to determine the LV Free Wall Profile (LVFWP)which consists of two circular arcs and a tangent to the arcs.R₂=D_(maj)/2 and AE=AB−EB. Thus, LVFWP depends solely on cardiacmeasurements.

To generate the 3-D shell in FIG. 2 b, the LVFWP was swept about theaxis in a non-axis-symmetric way. Let the LVFWP be the curve given byR_(p)(Z) where R_(p) is the distance from the axis and Z is the heightalong the axis (with Z=0 at the apex). The shell surface is given by${R\left( {\theta,Z} \right)} = {\left( {{\cos\quad\theta} + {\frac{D_{\min}}{D_{maj}}\sin\quad\theta}} \right){R_{P}(Z)}}$Note that LVFWP is the trajectory with θ=0. This is consistent withcardiac coordinates (as detailed in Streeter, 1979) wherein θ=0 is takenas the central longitude of the LV free wall. Cross-sections of theshell were elliptical with their ellipticity being similar to that ofthe epicardial boundary in the equatorial region.

Rigid foam sheets were cut according to digitally renderedcross-sections and fixed together to form a plug mold. A lay-up of epoxyreinforced with fiberglass was applied to the plug mold and sawed inhalf (lengthwise) after curing. Each half was fixed to a separable rightbutt joint and multiple coats of hard wax were applied. Upon laying-upwith fiberglass and a plywood cutout, the matching molds shown in FIG. 2f were formed. From these matching molds, the outer shell of the device(FIG. 2 c) was made from epoxy reinforced with fiberglass (using avacuum bag method to remove excess resin and to increase thefiber/matrix ratio).

A brass, right-angle, hose barb was attached to the apex after making ahole in the shell. It was sealed and fixed in place via an epoxy/aluminacomposite. A cigar-shaped latex membrane was draped over the edges andheld in place with a circumferential suture and cyanoacrylate glue.Suture loops were fastened out of nylon cord and affixed to the devicewith epoxy. Two profiles of the complete device are shown in FIGS. 2 d &22.

Example 2 Attachment of a DCCD to the Heart

Various methods of attaching the device to the heart have been testedusing the fixed heart that was measured in order to determine the sizeof the device. As shown in FIG. 3, the heart was sewn to the device withrunning sutures that go completely around the heart. Although this ismore laborious than a vacuum attachment method, other DCCDs require thedevice boundaries to be sutured to the heart and so a similar approachwas tried here.

For animal models of CHF, the attachment in FIG. 3 is likely to beacceptable. Yet in CHF patients, such a method of attachment would beprone to surgical complications because there is too much pericardialfat and because of the need to sew near important vascular structures(e.g. left and right coronary arteries, great cardiac vein and coronarysinus). Moreover, the coronary sinus and right coronary arteries are onthe posterior side of the heart, an area with limited exposure in-vivo.

To reduce the chances of surgical complications and to increase thespeed and ease of implantation, a second method of attachment wasdeveloped (see FIG. 4) using brief suture runs on the LV and RV freewalls, which are areas with good exposure, fewer primary vessels, andless pericardial fat. A posterior stent begins in the obliquepericardial sinus and goes through pericardial reflections to connectwith an anterior stent that lies in the transverse pericardial sinus.These stents keep the heart in the device via compression on the centerof the valve plane which includes the commissure of aortic, mitral, andtricuspid valves.

In order to make the implantation easier and eliminate the need toaccess the posterior side of the heart, an alternative stenting methodmay be used with just an anterior stent that pushes on the center of thevalve plane.

Example 3 Use of a DCCD

Experiments were performed using a device with an outer shell similar tothat of the Hewson patent containing a plexiglass window in the outershell to allow observation of the cardiac curvatures with a CCD camerawhile the device was in operation. The Hewson device was designed to beheld in place by contact forces between the rim and the heart, but evenactive hearts are soft tissues that can undergo high shear and squeezeout of the device. Specifically, the myocardium of hearts are organizedinto sheets that allow contracting myocytes to rearrange and shear toattain high radial motions.

Thus when the DCCD similar to the Hewson device was implanted in a youngbovine, even with a normal contractility, the heart readily escaped thedevice. Accordingly, the Hewson device, as described in the Hersonpatent, appears to be inoperable and required serious modification ofthe device and/or its means of attachment in order to develop anoperable device.

Specifically, these experiments showed that the valve plane of the heartmust be sewn to a Hewson type DCCD and then held in place with a stentthat reaches from the device through the transverse pericardial sinusand pushes down on the commisure of the aortic and bicuspid valves.Attachment was as described above in Example 2 with the second optionwherein the device was attached through partial suture to only theforward portion of the valve plane and not to the posterior as wellbecause of difficulties in accessing the posterior of the heart.

Attempts using the stent alone without attachment to the valve planewere not successful and caused mitral regurgitation and allowed much ofthe heart to escape the device. Even with attachment to the valve planeand use of a stent, tricuspid regurgitation occurred, but the heartremained within the device. Tricuspid regurgitation may be preventedthrough a variety of modifications, including the implantation of avalve support that attaches to the device through a more uniformattachment such as tenting and suturing to the atrial appendages. Use ofa fill suture to attach the device to the valve plane around the entireheart, rather than merely a partial suture as used in this experiment,may also prove beneficial.

More significantly, the DCCD, once able to retain the heart withinitself during contraction, was observed to preserve natural cardiaccurvatures.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the following claims.

1. A direct cardiac compression device that surrounds the heart andcomprising a compression means operable to actively promote acontraction strain pattern on a diseased or damaged myocardium thatpromotes beneficial growth and remodeling of the myocardium.
 2. Thedevice of claim 1, further comprising the contraction strain patterncharacterized by non-inversion or lack of gross perturbation of theheart's curvature.
 3. The device of claim 1, further comprising an outermember and at least one membrane inside the outer member.
 4. A directcardiac compression device that surrounds the heart and comprising acompression means operable to actively promote a contraction strainpattern on a diseased or damaged cardiac myocardium that reducesapoptosis in the myocardium.
 5. The device of claim 4, furthercomprising the contraction strain pattern characterized by non-inversionor lack of gross perturbation of the heart's curvature.
 6. The device ofclaim 4, further comprising an outer member and at least one membraneinside the outer member.
 7. A direct cardiac compression devicecomprising: an outer member; an inner membrane attached to the outermember; and fluid between the outer member and the inner membrane,wherein the fluid may be pressurized, and wherein and the device exertsa non curvature-inverting contraction stain pattern when used on aheart.
 8. The device of claim 7, further comprising the device installedaround the ventricular portion of the heart.
 9. The device of claim 7,further comprising the device anchored to the valve plane of the heart.10. The device of claim 7, further comprising a pneumatic drive operableto pressurize the fluid.
 11. The device of claim 7, wherein the outermember comprises an outer shell, membrane, or mesh.
 12. The device ofclaim 7, wherein the outer member comprises a rigid outer shell.
 13. Thedevice of claim 7, wherein the inner membrane comprises a biocompatiblematerial.
 14. The device of claim 13, wherein the biocompatible materialcomprises elastomeric polyurethane.
 15. A method of assisting a diseasedor damaged heart comprising providing a direct cardiac compressiondevice to the heart that compresses the heart during contraction withoutinverting or significantly perturbing the curvatures of the heart. 16.The method of claim 15, further comprising inducing ventricular recoveryin the heart.
 17. The method of claim 15, further comprising promotinggrowth and remodeling of the myocardium.
 18. The method of claim 15,further comprising preventing apoptosis of myocytes in the myocardium.19. The method of claim 15, further comprising preserving themyocardioum in a borderzone of a myocardial infarct.
 20. The method ofclaim 15, further comprising opening the chest cavity of a patient toprovide access to the heart; and attaching the device of to the valveplane of the heart.